1. Field of the Invention
The present invention relates to a spark timing control system for use in an internal combustion engine and, more particularly, to such a spark timing control system using a microprocessor with first and second read only memory means for storing signals representing spark advance and dwell angle values as a function of engine operating conditions.
2. Description of the Prior Art
With recent miniaturized computer technologh advancement, electronic spark timing control systems have been developed which include a mini-computer responsive to signals indicative of various engine operating parameters, such as engine speed and load, to calculate the required spark advance. Such electronic spark timing control systems perform stable spark advance calculations with close tolerances. In addition, they consume less space and have control accuracy relatively unaffected by changes in environment conditions, as compared to conventional engine speed responsive centrifugal and vacuum manifold responsive vacuum advance devices.
However, which such conventional electronic spark timing control systems it is difficult to provide highly accurate spark timing control for engine operating parameters and impossible to determine an optimum spark advance for each pair of engine speed and load values if handling exhaust gas recirculation rate or other engine operating parameters are not given in an arithmetic expression. The reason for this is that the conventional minicomputer spark timing control systems are substantially similar in function to the conventional mechanical control device except that spark advance calculations are performed electrically rather than mechanically, i.e. the prior art minicomputer systems are basically electronic analogs of the mechanical systems.